Madison Reporter

According to a new study of rivers and lakes in Wisconsin, natural foams from these bodies of water contain much higher concentrations of per- and polyfluoroalkyl substances (PFAS) than the water below them.

Thirty-six different kinds of PFAS compounds were analyzed in samples of both the foams and water surface microlayers of 43 Wisconsin rivers and lakes. The study, published in Environmental Science & Technology, also revealed that foams, generally off-white and found along shorelines, are not necessarily an indicator of elevated contamination levels in the entire water body.

“We studied many different lakes and found PFAS in all of them. The PFAS concentrations were high in the foams even if the concentrations in the water were relatively low,” said Christy Remucal, a professor with the University of Wisconsin–Madison Department of Civil and Environmental Engineering and interim director of the University of Wisconsin Aquatic Sciences Center.

Remucal stressed the need to avoid the foams because of the contaminants’ warning-worthy levels. “The chemical we found most in the foam is PFOS, which is one of the PFAS chemicals that is driving fish advisories and drinking water regulations,” she said. “The highest PFOS concentrations we measured in foam were almost 300,000 nanograms per liter and, for comparison, the federal drinking water regulation is 4 nanograms per liter.”

She continued, “The main way people are exposed to PFAS is through ingestion…Obviously, people aren’t drinking foam. I would be more concerned about, for example, a kid who plays in the foam and then goes to grab a handful of snacks. You could potentially have some oral exposure that way.”

There are more than 9,000 different PFAS compounds, often referred to as “forever chemicals” because some do not readily break down in the environment. For decades, they have been used to make products resistant to water, grease, oil and stains. They are also found in some types of firefighting foams—a major source of environmental contamination. Exposure to high concentrations has been shown to have adverse effects on human health including higher incidence of cancer.

The levels observed validate a current Wisconsin Department of Natural Resources warning as well as similar warnings issued for freshwater foam in Michigan and saltwater foam in the Netherlands. These cautions come as spring and summer approach Wisconsin when people spend more time near open water or engaging in activities where foams can be found.

The study by Remucal; postdoctoral co-investigators Summer Sherman-Bertinetti and Sarah Balgooyen; along with graduate students Kaitlyn Gruber and Edward Kostelnik was funded by a grant from the Wisconsin Sea Grant College Program.

Integral to this research were dozens of citizen volunteers and assistance from the Wisconsin Department of Natural Resources who alerted researchers to foam presence—critical since sampling was opportunistic due to foam’s fleeting nature.

While high contamination levels in foams are pressing findings from this study, Remucal's team also discovered slightly higher PFAS levels in samples from water surface microlayers compared to underlying waters. Studying these microlayers helps understand how PFAS move between groundwater and surface waters.

This work contributes to global efforts exploring possible paths for PFAS cleanup. Because these substances are surfactants drawn to air-water interfaces like bubbles forming foam—concentrated contaminants might be removed effectively when captured this way.